The newest version of Google Identity Toolkit has been released as Firebase Authentication. It includes upgraded client SDKs, open source UI libraries, session management and integrated email sending service for forgotten password flows.

New projects should use Firebase Authentication. To migrate an existing project from Identity Toolkit to Firebase Authentication, see the migration guide.

Set up dual write for new users

Overview

To migrate your site to use Identity Toolkit v3 for authentication, it is possible to maintain full
availability by first enabling dual write for any changes. This means if a new user signs up, the
record is created in both your existing database and the Identity Toolkit v3 database.

Implementing dual write

Here you will modify the existing logic in your new account flow to dual-write to your local account
database and to the Identity Toolkit back end. This will be achieved with the Upload Account API

You will need to set up a Service Account (as described in the Configure Service step)
and use the uploadAccount API to write entries to Identity Toolkit. This is easiest if done by using
the per-language libraries included with the quick-start apps. Each includes a README
file to describe how to upload accounts in that language.

You will need to write these entries to each database serially, first into your local account
database and retrieve your localId and then push this value to Identity Toolkit to maintain a
consistent key. You need to set up this dual-writing system regardless of the method new users are
signing up for your app: web or mobile, password or IDP sign-ups. Keep track of what time you have
this fully rolled out to help you understand how to manage the user upload process.